When writer-producer Oren Peli is talking about the thing he loves most -- horror movies -- he's like a child opening gifts on Christmas Day. His eyes light up, and it's obvious this is something he'd be more than happy to talk about all day long.

You probably know about Peli's feature film debut "Paranormal Activity," which he wrote and directed; last we heard, it made a bajillion dollars and got two sequels (and counting!). Peli wrote and produced the new horror movie "Chernobyl Diaries," about six tourists who get stranded in a city called Pripyat, one of the cities in Chernobyl that were affected in the nuclear explosion in 1986. Peli sat down with us to talk about how the film's dialogue was improvised, why he didn't direct the film himself and how he tried to approach the sensitive subject matter.

You've written a film based on an original idea, and "Chernobyl Diaries" is an idea based on a real catastrophe. Which do you find more challenging?

Well, everything has their own challenge. The real challenge here was a blessing and a curse. We felt like the Chernobyl incident, in its abandoned state, the people really do go over to do tours there, [so] it was already kind of like a great foundation for the story. But at the same time you want to do it justice -- you're not just creating a fictional place, you have to re-create a location. It was very important for us and for the director [Bradley Parker] that visually (and [with] the story) we get as many of the details right. The movie is obviously fictional. We're not trying to say it's a documentary. We wanted it to have a very realistic and plausible foundation. So that definitely makes it very challenging.

What steps did you take when writing to keep it entertaining while being mindful of the real and awful things that happened?

We don't think that [the film] needs to be taken seriously -- it's just a horror movie, and we're hoping people will see it as nothing more than that. There are definitely scenes we could have gone a lot further, and there are different directions we could have gone to as far as the marketing and the film itself that we decided not to go. We're very happy what we end up with. I think most people see it for what it is.

I've seen a few people very vocal, but a very small minority have problems with the movie or with the concept -- in many cases they haven't even seen the movie. I think that if you find the subject matter insensitive, nobody is going to force you to see it. We actually had people from a children of Chernobyl charity who saw a cut of the movie and were very impressed with the way we recreated Pripyat because they are very familiar with it and they didn't think we were insensitive at all. In fact, they were very happy because [the film] raises awareness for Chernobyl which -- to some degree some of us still remember it, but for the new generation that's not familiar with it at all, it's not being talked about again. They're actually very excited people are talking about it again and it's back in the consciousness of people.

With "Chernobyl Diaries" you're taking a big chance with a first-time director. What was it about Brad Parker that led you to believe he was going to create the vision you had when you were writing this?

It was definitely a little scary, because when we met Brad the first time we were blown away by how smart he was and how he was on the same page as us as far as our approach to bringing the movie to life. We had extreme confidence in his ability technically because he's been a commercial director and second unit director for many years. He's done just about anything [a director] can do except direct a feature.

You've written and directed your own material, and the first thing you directed was a huge hit. Why did you decided to pass the torch as far as directing goes?

When it came to this particular project, I was having dinner with a friend of mine ["Chernobyl Diaries" producer Brian Witten] and I said, "You know what would be a really scary horror movie? If a group of people went to Chernobyl and they got stuck there and all of this crazy stuff happens." And he was like, "Aww! This is awesome, we should do it!" And I said, "No no no, I wasn't talking about doing it -- I just thought it could be a cool idea." He kept saying we had to do it and I kept saying, "I can't commit to directing anything right now, leave me alone!" [laughs] And he just wouldn't drop it, and he said, "Look, you don't have to direct it. We'll get another director. You won't have to do anything. I'll do all of the producing -- just write the basic story and we'll take it from there."

He finally talked me into it, and I ended up being more involved than I thought I would be. I feel I wouldn't have been able to commit to directing it, and I became much more involved as a producer than I thought I would be. Brian did take a lot of the burden of being a producer off of me, so between him and Brad directing, I was still was able to become an integral part of the process.

Talk about the location where the movie takes place -- it felt like a character in the film.

Basically the reason why the movie exists is because of Pripyat, so we knew we had to set it up appropriately for the story and also when you're there re-creating it, so you really get the sense of being alone in an abandoned and forgotten town. A lot of it had to do with setting it up. The character of Uri [played by Dimitri Diatchenko] was really important as the guide who takes you there and the way the characters think, "Oh this is just a fun trip," and once they're there they are taken aback by the gravity of the situation. It kind of hits them and stops being fun. You can see them really not knowing how to feel about it. Then the movie changes. There's a lot of things we had to do to set up the set; a lot of it was in the sound design -- we stripped away the sound of a city full of life. There's no source of sound at all except maybe the wind and your own footsteps.

Without giving anything away, the things that we do see in the movie, that was all practical effects, right?

It was a combination of both.

How do you balance using CGI and using practical effects?

That's one of the reasons why we were so lucky to have Brad. With his background of being a visual supervisor, he knew what kind of things we needed to depend on practical effects for. In many cases, more than you realize, when it comes to the set, it's a combination of practical effects and visual effects. I'll give you an example: The Ferris wheel, we only built the bottom quarter of it. Everything else, when the camera pans up or when you see it in the background, is extended digitally. Brad would always know in advance, "We only need to build this," or "We only need to do this kind of makeup effect." He had the ability to make those kind of decisions and it all worked amazingly well.

I read in the press notes that there was a lot of improvising. When you've written a full script and the actors are improvising, how do you keep a steady flow of where the script needs to go?

What we had originally was a treatment which was basically the whole story without any dialogue. So it would say, "Paul goes to Chris, 'Let's go over there.'" It wasn't exact dialogue. And then we gave it to the actors after they were brought on board, and then we brought in two more writers [Shane and Carey Van Dyke] to flesh out the dialogue ... Then once we had the full script with the dialogue, we gave it to the actors and said, "Okay, this is the script, but you don't have to really stick to it. This is the general idea."

... In other cases, there were some complex scenes that we'd have all the actors get together during rehearsal -- sometimes it was even during auditions -- [and] we would let them totally improvise the entire scene and we would have the video camera recording and would later be like, wow, this particular take or moment felt very natural and super authentic, and what we would do was actually transcribe the actual dialogue they came up with and put it into the script. So then the script would have dialogue that was their own improvisation. They would then read it back and it was their own voice, versus a writer forcing words into their mouth. So I think that's why a lot of the dialogue in the movie feels very authentic.